I’ve really enjoyed the kickstart.nvim template. Everything is clear and documented and it’s helped me set neovim the way I want to.
For the LSP side, I’m passing the tools I need from home-manager like this and in neovim I it check if I’m in NixOS like this so it doesn’t install the tools through Mason, but still load them in lsp-config. The advantage of doing this is that my config is portable in other distros where Mason will download the tools I need.
There is kickstart-nix.nvim which is based on kickstart.nvim and is tailored to run on Nix out of the gate, so I suggest you take a look at that first if you want something simple that just works.